You do have a Void type in Java if you really must specify a return type and don't want to return anything e.g. services and their tasks in JavaFx. The Task must have a return type thus you can use Void if the task doesn't actually return anything.
Been using Fastmail for like 10 years and their service has been superb. Planning to move to a provider within the EU. Probably Mailbox as Tuta doesn't, at the moment, have a move your stuff from a previous provider service.
No google on device no tracking, and I don't use google services anyhow (with first party clients anyhow). I do have google play services installed but no google account so they don't have an identity to connect the data they might be able to collect from the phone. Only google service I use is youtube but that's with third party clients only (FreeTube & NewPipe) over vpn of course.
It's good to keep pounding this info to normies. Maybe they'll understand one day.